Significance: The etiology and pathogenesis of many of the most important ear disorders remain poorly understood at the cellular and molecular level. Although many genes underlying hereditary auditory and vestibular disorders have been identified, much remains to be learned about the exact function of each gene and how their mutations result in ear pathology. The significance of the current proposal is that it incorporates modern molecular biology and imaging techniques to study temporal bones. These techniques will add a new dimension to the understanding of the etio-pathogenesis of important ear disorders. A consortium of temporal bone centers will greatly enhance the data and resource sharing and will undoubtedly promote collaborations. The long-term objective of this proposal is to apply cell and molecular biology techniques to maximize nucleic acid yield from the human temporal bones, thereby allowing elucidation of the mechanisms involved in the pathogenesis of ear diseases at the molecular level. The Specific Aims of this study are as follows: Specific Aim 1: To increase the number of temporal bone pledges from select ear diseases and to develop specimen- processing techniques for future temporal bone acquisitions, as well as protocols for bones currently in the HEI collection, that will allow the application of molecular biology techniques to the study of temporal bones. Specific Aim 2: To apply modern imaging techniques to visualize temporal bones for stereology, morphometry and three-dimensional reconstruction. Specific Aim 3: To increase the quality of clinical information accompanying each donated temporal bone by performing audiometric and/or vestibular function tests at regular intervals. Specific Aim 4: To increase the access to human temporal bone specimens by researchers. Specific Aim 5: To be an integral member of the Human Temporal Bone Consortium, collaborate with the Registry and participate in the development of standardized processing protocols, as well as in the sharing of data and clinical assessments with the Consortium members and the Registry. Specific Aim 6: To encourage collaborations with investigators who have little experience using human temporal bones. Specific Aim 7: To encourage participation of young scientists in temporal bone research.